The field of this invention relates to methods and apparatus for heating and melting a material charge in a furnace, particularly of the type used in heating and melting a non-ferrous material utilizing a liquid fuel.
In the prior art, there are many types of vertical furnace arrangements that have been used for melting various types of charge materials under a wide variety of different circumstances, such as the typical units disclosed in U.S. Pat. Nos. 2,203,163; 2,815,278; 2,886,304; 3,148,973; 3,199,977; 3,603,571; and 3,958,919. U.S. Pat. Nos. 3,715,203; 3,788,623; and, 3,809,378 generally disclose specific types of furnace arrangements that are particularly useful in melting non-ferrous metals.
However, within the prior art directed towards burners and their specific structural configurations, many varying types of burners have been designed to operate under a wide variety of particular applications and environments for use in heating a material charge having various individual characteristics. Such burners include those as disclosed in U.S. Pat. Nos. 2,605,180; 3,701,517; and 3,852,021. However, due to recent price increases and the widespread nonavailability of the cleaner gaseous fuels, it has become desirable to be able to burn various grades of fuel oils with such burners to provide the appropriate heating necessary for heating and melting a material charge within a furnace. Many attempts have been made at providing an effective, liquid fuel burner, such as those disclosed in U.S. Pat. Nos. 2,632,501; 2,697,910; 2,698,050; 2,711,214; and, 3,366,469. Further, other attempts in providing liquid fuel types of burners are disclosed in U.S. Pat. Nos. 2,205,983; 2,333,531; 2,632,300; 2,725,929; 3,042,105; 3,558,119; 3,749,548; 3,758,263; 3,777,983; 3,947,226; 3,980,415; 3,986,815; and 4,025,282.
However, despite the significant amount of art in the liquid fuel burner-furnace arrangements, so far as known, it has been a continuous problem that liquid fuel burners have not been able to effectively vaporize and substantially combust all of the liquid fuel prior to contacting the material charge within the furnace. When heating and melting non-ferrous materials, such as copper and aluminum, the vaporization and substantial combustion of the liquid fuel prior to contacting the material charge becomes of critical importance for maintaining control of the metallurgical quality of the melt; for, if droplets of liquid fuel actually contact the relatively cool surfaces of the material to be melted, the melt will preferentially remove oxygen from the gas stream leaving the liquid fuel uncombusted, resulting in a melted charge that is contaminated with the oxygen and some uncombusted liquid fuel. This contamination of the charge increases in severity as the grades of fuel oil being used to fire such a furnace are reduced. Therefore, it has been a significant problem in this art to utilize the more desirable, low cost, low grades of liquid fuels for heating non-ferrous materials without contaminating the melt with the liquid fuels that escape combusting prior to contacting the material charge to be melted.